Mine does it too sometimes. But not often, and usually only on packs which are old and have become unmatched. (ie some cells can already be done at .9v, others are still stuck up around 1.2v) Usually though if I leave it long enough it will finish, or else I will discharge that cell by itself on the charger.
It can be a pain in the ass I know..
All in all though, I think the DPD is a good unit, all be it sometimes slow.
Associated TC6.1 | Hobbywing V3 | LRP X12 | Spektrum | Futaba | Reedy